I removed the old nut as you suggested with wire cutters in the video, removed the old seal with an O- ring pick & pushed the new seal in with a small metal tube, had to hold the shaft with pliers while pushing the new nut in because of some back & forth play in the shaft so the nut would be firmly against the seal. There was no leak after putting it all back together and running a few test.
Seems like a lot of money for such small parts but understand it would have cost a lot more to have an appliance repairman to do the job. All in all very satisfied with the results.